The invention relates to the production of industrial chemicals. More specifically, the invention relates to the production of metal chlorates by the reaction of ammonium chlorate with metal carbonates/bicarbonates at elevated temperatures. The invention also relates to the production of ammonium chlorate using by-product solid ammonium bicarbonate and aqueous solution of sodium chlorate.
Metal chlorates have been used for a long time as a main raw material in the manufacture of fireworks and matches. Potassium chlorate is also one of the main raw materials in the production of charcoal briquettes and as a pure oxygen generator. Potassium chlorate is a very important worldwide commodity for these purposes.
Existing technologies for commercial production of potassium chlorate involves the use of sodium chlorate/potassium chloride as described in U.S. Pat. Nos. 4,339,312 and 5,087,334. The process of U.S. Pat. No. 5,087,334 involves the double displacement reaction of sodium chlorate and potassium chloride. There are several drawbacks to this process, however. For instance, the double displacement reaction of sodium chlorate and potassium chloride seldomly yields a pure potassium chlorate. Because sodium chlorate and sodium chloride are hygroscopic, the presence of these impurities decreases the burning capabilities of the fireworks, matches, and charcoal briquettes in which the potassium chlorate is included. Moreover, the high moisture content of the sodium chlorate and sodium chloride causes the production of noxious chemicals, such as hydrochloric acid, at high temperatures.
U.S. Pat. No. 4,339,312 describes direct electrolysis of potassium chloride. While electrolysis is often successful in producing pure potassium chlorate, the process is expensive because of the high cost of potassium chloride.
It is therefore a primary objective of the present invention to provide an improved method of producing metal chlorates.
It is a further objective of the present invention to provide an improved method of producing metal chlorates that is simple and environmentally safe.
It is yet a further objective of the present invention to provide a method of producing metal chlorates whereby the waste by-product of the process may be recycled to produce a useful chemical.
It is still a further objective of the present invention to provide a method of producing metal chlorates whereby the resulting metal chlorate is substantially free of impurities.
It is a further objective of the present invention to provide a method of producing non-metal chlorates using waste by-products from the novel metal chlorate production method described herein.
These and other objectives will become apparent from the following description.
The present invention describes a method of producing metal chlorate through the reaction of metal carbonates/bicarbonates with ammonium chlorate. The reaction is performed in an aqueous medium at elevated temperature under reduced/normal pressure. Evaporation of the reaction mixture produces ammonia and carbon dioxide by-products and a pure metal chlorate. Alternatively, the gaseous ammonia and carbon dioxide by-products can be condensed with water and carbon dioxide to produce ammonium bicarbonate. This ammonium bicarbonate may in turn be used to produce ammonium chlorate by reacting the ammonium bicarbonate with sodium chlorate. The ammonium chlorate can be recycled to produce metal chlorate in accordance with this invention, while the sodium bicarbonate by-product may be used in the production of various industrial chemicals.
As set forth above, the present invention discloses a novel method of producing metal chlorate through the reaction of metal carbonates/bicarbonates with ammonium chlorate.
Any source of ammonium chlorate is suitable for use in this invention. The ammonium chlorate is preferably prepared by the double decomposition reaction of ammonium sulfate and barium chlorate. The most preferred source of ammonium chlorate is that produced by the reaction of ammonia and carbon dioxide, as described in U.S. Pat. No. 5,948,380, by the process described in this invention.
Any Group I metal carbonate or bicarbonate is suitable for use in this invention, including lithium, sodium, potassium, rubidium, and cesium carbonates and bicarbonates. Preferred metal carbonates and bicarbonates for use in this invention are those of lithium and potassium.
The metal carbonate/bicarbonate is combined with the ammonium chlorate in a molar ratio of about 1:1 in the case of metal bicarbonates and, in the case of metal carbonates, in a ratio of about 1:2. While the metal carbonate/bicarbonate and ammonium chlorate may be combined in any quantities or ratios, their combination will still result in the 1:1 and 1:2 stoichiometric ratios described above. The reaction proceeds as shown in the following chemical equation:
xe2x80x83NH4ClO3+MHCO3xe2x86x92MClO3+NH3+CO2+H2Oxe2x80x83xe2x80x83(1A)

Wherein M=a Group I metal (column 1 element of the periodic table).
The temperature range of the reaction is not critical, and may range from about 5-120xc2x0 C. The preferred reaction temperature is about 35-80xc2x0 C. The reaction preferably takes place in aqueous solution under reduced/normal pressure. The reaction is allowed to proceed until most of the liquid in the mixture is evaporated. The liquid may be collected as solid/slurried aqueous ammonium bicarbonate. The solid remaining is pure metal chlorate. Alternatively, the gaseous by-products of ammonia and carbon dioxide may be collected under at reduced to elevated pressure in a range of from 76-7600 mm/Hg, then condensed with water and carbon dioxide to produce ammonium bicarbonate. Excess carbon dioxide may be in the form of dry ice, liquid, or gas. The condensation process may be carried out in a temperature range of between about xe2x88x9278xc2x0 C. to 45xc2x0 C. These reactions are set forth in equations 2 and 3: 
The ammonium bicarbonate by-product manufactured in accordance with this invention, or any other source of ammonium bicarbonate, may be used in preparing ammonium chlorate, that in turn may be recycled to produce metal chlorates as described above. Solid/slurried ammonium bicarbonate is added to about a 1M to saturated solution of equal moles of sodium chlorate. The ammonium bicarbonate and sodium chlorate are mixed to make a fine slurry. The mixing preferably takes place at a temperature range of between about xe2x88x925xc2x0 C. to 50xc2x0 C., with the a preferred temperature range of 15-30xc2x0 C. and a most preferred temperature of 20-25xc2x0 C.
Once the compounds have had sufficient time (about 4-8 hours) to equilibrate, a fine crystalline/powder sodium bicarbonate is precipitated. The solid sodium bicarbonate may be separated using conventional techniques such as by commercially available filtration or centrifugation device. The ammonium chlorate-containing filtrate may then be recycled in the preparation of metal chlorates as set forth in equation 1.
The following examples are offered to illustrate but not limit the invention. Thus, they are presented with the understanding that various formulation modifications as well as reactor modifications may be made and still be within the spirit of the invention.